Stress induced diffusion along adhesional contact interfaces Original Research Article

The stress induced vacancy diffusion process along the bond (contact) interface between fine gold wires is numerically analyzed. The elastic stress due to the adhesional contact induces vacancy diffusion even at room temperaturs. Because of low temperatures, it is assumed in the numerical simulation that the vacancy diffusion along the adhesional contact interface (boundary self-diffusion) is predominantly produced. The residual stress is produced around the contact interface due to the adhesional elastic bonding. The stress relaxation process where the residual stress is gradually reduced by the vacancy diffusion along the interface is numerically simulated. The rate of stress relaxation increases with decreasing the radius of wire but the growth of contact width due to the vacancy diffusion during (and after) bonding is scarcely produced. It is, therefore, suggested from the numerical results that the increase of the bond strength, with time, can be governed by the relaxation process of the residual stress. Further, the activation energy for the mechanism which increases the bond-strength is experimentally obtained.